[xen staging] x86/vm_event: Carry the vmtrace buffer position in vm_event

[patchbot@xxxxxxx]

commit c5866ab93167a73a8d4d85b844edf4aa364a1aaa
Author:     Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
AuthorDate: Mon Jan 18 12:46:37 2021 -0500
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Feb 5 17:37:28 2021 +0000

    x86/vm_event: Carry the vmtrace buffer position in vm_event
    
    Add vmtrace_pos field to x86 regs in vm_event. Initialized to ~0 if
    vmtrace is not in use.
    
    Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
---
 xen/arch/x86/vm_event.c       | 3 +++
 xen/include/public/vm_event.h | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/xen/arch/x86/vm_event.c b/xen/arch/x86/vm_event.c
index 848d69c1b0..36272e9316 100644
--- a/xen/arch/x86/vm_event.c
+++ b/xen/arch/x86/vm_event.c
@@ -251,6 +251,9 @@ void vm_event_fill_regs(vm_event_request_t *req)
 
     req->data.regs.x86.shadow_gs = ctxt.shadow_gs;
     req->data.regs.x86.dr6 = ctxt.dr6;
+
+    if ( hvm_vmtrace_output_position(curr, &req->data.regs.x86.vmtrace_pos) != 
1 )
+        req->data.regs.x86.vmtrace_pos = ~0;
 #endif
 }
 
diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
index 141ea024a3..147dc3ea73 100644
--- a/xen/include/public/vm_event.h
+++ b/xen/include/public/vm_event.h
@@ -223,6 +223,13 @@ struct vm_event_regs_x86 {
      */
     uint64_t npt_base;
 
+    /*
+     * Current position in the vmtrace buffer, or ~0 if vmtrace is not active.
+     *
+     * For Intel Processor Trace, it is the upper half of MSR_RTIT_OUTPUT_MASK.
+     */
+    uint64_t vmtrace_pos;
+
     uint32_t cs_base;
     uint32_t ss_base;
     uint32_t ds_base;
--
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